Nice work & try with rubber bands instead of rope ( they need to be stretched till the box
would have then the possibility to swing at very low cycles....2-3 Hz are subsonic frequencies and well out of band )

* How did you design / calculate it?
* What is the Qts of the resulting driver/voltage?
* What is the lower cutoff in-room (e.g., 60hz or 50Hz or ...?)
* Details of the amp?
* What is your rationale for skipping a back-chamber perhaps?

Nice work & try with rubber bands instead of rope ( they need to be stretched till the box
would have then the possibility to swing at very low cycles....2-3 Hz are subsonic frequencies and well out of band )

Very cool design. Do you use stuffing inside or find that too much higher frequencies get through the horn since it is so smooth?

To make the sound smooth.....smoother inside tunnel sound better.
I using sand paper hand sand, 200,320,600 then 1200.....and take time!
Some old wrinkle paper had been add inside the throat area.
Personal, I prefer inside empty, or less absorb material, to keep the music detail as much as possible.